Can Dermal Fibrosis and Telangiectasia Occur on the Sacrum?
Yes, dermal fibrosis and telangiectasia can absolutely be seen on the sacrum, particularly as late complications of pelvic radiotherapy, since the sacrum contains 14% of the body's active bone marrow and is frequently included in pelvic radiation fields. 1
Radiation-Induced Changes on the Sacrum
Mechanism and Timeline
Chronic radiation-induced skin changes are characterized by dermal fibrosis, telangiectasia formation, and damage to elastic fibers in the dermis. 1
Telangiectasia from radiation has a threshold dose of 10 Gy with onset typically greater than 1 year post-exposure. 1
Induration (invasive fibrosis) also has a threshold of 10 Gy, though the onset timeline varies. 1
Specific Context: Pelvic Radiotherapy
The sacrum represents 14% of total body bone marrow distribution and is routinely included in pelvic radiation treatment volumes for gynecologic malignancies. 1
RT-related vaginal and rectal morbidity is characterized by microcirculatory alterations leading to telangiectasia and fibrosis in irradiated tissues. 1
Chronic radiation proctitis is histologically characterized by submucosal connective tissue fibrosis and neoangiogenesis followed by telangiectasias. 1
Clinical Presentation
Radiation-induced skin injury can be identified by its temporal pattern (developing months to years after irradiation) and location at the beam entrance site. 1
If the beam is positioned over a single skin site for prolonged periods, the lesion will be well-demarcated with a shape consistent with the collimated beam. 1
Important Clinical Caveats
Risk Factors for Enhanced Radiation Sensitivity
Patients with collagen vascular disease (particularly scleroderma, discoid lupus erythematosus, and mixed connective tissue disease), diabetes mellitus, and hyperthyroidism are more susceptible to radiation injury. 1
Patients homozygous for ataxia telangiectasia are known to be more radiosensitive. 1
Previous radiation therapy or fluoroscopic procedures lower the threshold for radiation injury in subsequent exposures. 1
Differential Considerations for Sacral Skin Findings
While radiation-induced changes are the primary concern in patients with radiation history, other sacral skin findings should be distinguished:
Lumbosacral dermal sinus tracts (DSTs) are located on the flat part of the sacrum and may be associated with surrounding vascular anomalies, but these are congenital malformations, not acquired fibrotic changes. 1
Innocent coccygeal dimples are located at or below the gluteal cleft line and are not associated with pathologic changes. 1
Monitoring and Management
Patients who undergo pelvic radiotherapy should be monitored for late toxicity with systematic follow-up by a multidisciplinary team. 1
The median time to radiation-induced complications ranges from 8 to 39 months after radiation therapy, though telangiectasia specifically develops after 1 year. 1, 2
Conservative management is the primary approach for radiation-induced tissue changes, with bone-directed therapies used in only 6% of cases when skeletal complications develop. 2